Projection assembly for a head-up display

Abstract

The invention relates to a projection assembly for a head-up display (HUD), comprising a composite pane (10) and an imaging unit (4). The composite pane (10) is provided with a sun protection coating (20), comprising a first dielectric layer or layer sequence (M1), a first electrically conductive layer (21.1) with a thickness of 6 nm to 10 nm, a second dielectric layer or layer sequence (M2), a second electrically conductive layer (21.2) with a thickness of 6 nm to 10 nm, a third dielectric layer or layer sequence (M3), a third electrically conductive layer (21.3) with a thickness of 10 nm to 15 nm, and a fourth dielectric layer or layer sequence (M4), which are arranged in a specified order starting from the substrate, wherein the ratio between the thickness of the second electrically conductive layer (21.2) and the thickness of the first electrically conductive layer (21.1) is 0.9 to 1.3, the ratio between the thickness of the second electrically conductive (21.2) and the thickness of the third electrically conductive layer (21.3) is 0.5 to 1.0, and the ratio between the thickness of the first electrically conductive layer (21.1) and the thickness of the third electrically conductive layer (21.3) is 0.5 to 1.0.

Description

[0001] Projection arrangement for a head-up display

[0002] The invention relates to a projection arrangement for a head-up display.

[0003] Modern automobiles are increasingly being equipped with so-called head-up displays (HUDs). Using a projector, typically located in the dashboard, images are projected onto the windshield, reflected there, and perceived by the driver as a virtual image (as seen from the driver's perspective) behind the windshield. This allows important information to be projected into the driver's field of vision, such as the current speed, navigation information, or warnings, which the driver can perceive without having to take their eyes off the road. Head-up displays can thus significantly contribute to improving road safety.

[0004] HUD projectors typically illuminate the windshield at an angle of incidence of approximately 65%, which is close to the Brewster angle for an air-to-glass interface (57.2° for soda-lime glass). Two projection principles are particularly common:

[0005] The HUD projector operates with s-polarized radiation. The projector radiation is reflected off both external surfaces of the windshield. This results in a slightly offset secondary image, the so-called "ghost image," appearing alongside the desired main image. This problem is typically mitigated by arranging the surfaces at an angle to each other, particularly by using a wedge-like intermediate layer to laminate the windshields, which are designed as a composite pane, so that the main image and the ghost image are superimposed. Laminated glass with wedge films for HUDs are known, for example, from WO2009071135A1, EP1800855B1, or EP1880243A2.

[0006] - The HUD projector is operated with p-polarized radiation. Due to the angle of incidence near the Brewster angle, no significant reflection occurs at the glass surfaces. Instead, the windshield is equipped with a reflective layer designed to reflect the projector radiation. Since the significant reflection occurs at only one interface (namely the reflective layer), no ghosting occurs. Examples include DE102014220189A1, EP3187917B1, and WO2021104800A1.

[0007] Windshields are often equipped with a sun protection coating to reflect infrared components of the sun's radiation and thereby reduce the energy input into the vehicle. Typically, the sun protection coatings are stacks of thin layers with multiple silver layers. Reference is made to US20070082219A1, WO2013104438A1 and WO2013104439A1 for example. Such a sun protection coating represents an additional reflection surface for the radiation of the HUD projector, thereby creating an additional ghost image. In the case of a p-polarized HUD, the sun protection coating can in principle be used as a reflection layer. However, the two applications place different demands on the coating: a sun protection coating that is optimized for good IR-reflecting effect does not generally produce a high-intensity and color-neutral HUD display.Even with p-polarized HUDs, it will often be desirable to combine a reflective layer with a sunscreen coating, so that the problem of ghosting also occurs here.

[0008] There is therefore a need for solar control coatings that are compatible with HUD projection systems and, in particular, have a low reflectance to the radiation of the HUD projector, regardless of whether it is operated with s-polarized, p-polarized or mixed-polarized radiation.

[0009] A projection system operated with p-polarized radiation is known from CN114349371 B. The composite pane is equipped with a dielectric reflective layer for reflecting the p-polarized radiation and with an additional sunscreen coating with at least one silver layer.

[0010] The invention is based on the object of providing an improved projection arrangement for a head-up display, comprising a composite pane which is irradiated by an imaging unit to generate the display image and which is equipped with a sun protection coating. The sun protection coating should, on the one hand, have a good IR-reflecting effect and ensure a low energy input through the composite pane. On the other hand, the sun protection coating should have a low reflectance with respect to the radiation from the imaging unit, so that it does not cause a disturbing ghost image, regardless of whether the imaging unit is operated with s-polarized or p-polarized radiation. Furthermore, the composite pane should have a low external reflectance and neutral reflection colors. The object of the present invention is achieved according to the invention by a projection arrangement according to claim 1.Preferred embodiments emerge from the subclaims.

[0011] The projection arrangement according to the invention for a head-up display (HUD) comprises at least one composite pane and an imaging unit. As is usual with HUDs, the imaging unit irradiates an area of ​​the composite pane, where the radiation is reflected toward the viewer (driver), creating a virtual image that the viewer perceives from behind the composite pane. The area of ​​the composite pane that can be irradiated or is irradiated by the imaging unit is referred to as the HUD area. The imaging unit is therefore directed toward this HUD area. A projector is usually used as the imaging unit, with the beam direction being varied by mirrors, particularly vertically, in order to adapt the projection to the viewer's height. The area in which the viewer's eyes must be located with a given mirror position is referred to as the eyebox window.This eyebox window can be moved vertically by adjusting the mirrors, with the entire accessible area (i.e., the overlap of all possible eyebox windows) being referred to as the eyebox. A viewer located within the eyebox can perceive the virtual image. This, of course, means that the viewer's eyes must be located within the eyebox, not their entire body.

[0012] The technical terms used here from the field of HUDs are generally familiar to those skilled in the art. For a detailed description, please refer to the dissertation "Simulation-based Measurement Technology for Testing Head-Up Displays" by Alexander Neumann at the Institute of Computer Science at the Technical University of Munich (Munich: University Library of the Technical University of Munich, 2012), particularly Chapter 2, "The Head-Up Display."

[0013] The composite pane comprises an outer pane and an inner pane which are joined together by a thermoplastic intermediate layer. The composite pane is intended to separate the interior from the outside environment in a window opening, in particular the window opening of a vehicle. In the sense of the invention, the inner pane refers to the pane of the composite pane facing the interior (in particular the vehicle interior). The outer pane refers to the pane facing the outside environment. The composite pane according to the invention is preferably a windshield (front window) of a vehicle on land, in water or in the air, in particular the windshield of a motor vehicle, for example a passenger car or truck, or the front window of an aircraft, ship or rail vehicle, in particular a train.HUDs in which the projector beam is reflected off a windshield to create an image perceivable by the driver (viewer) are particularly common. In principle, however, it is also conceivable to project the HUD onto other windows, particularly vehicle windows, such as a side window or rear window. The HUD on a side window can, for example, highlight people or other vehicles with which a collision is imminent, provided their position is detected by cameras or other sensors. A HUD on a rear window can provide information for the driver when reversing.

[0014] The laminated glass has a top edge and a bottom edge, as well as two side edges running between them. The top edge refers to the edge that is intended to face upwards when installed. The bottom edge refers to the edge that is intended to face downwards when installed. In the case of a windshield, the top edge is often referred to as the roof edge, and the bottom edge is often referred to as the engine edge.

[0015] The outer pane and the inner pane each have an outer surface and an inner surface, and a circumferential side edge running between them. For the purposes of the invention, the "outer surface" refers to the main surface intended to face the outside environment in the installed position. For the purposes of the invention, the "inner surface" refers to the main surface intended to face the interior in the installed position. The interior-side surface of the outer pane and the outer surface of the inner pane face each other and are connected by the thermoplastic intermediate layer.

[0016] According to the invention, the composite pane is provided with a solar control coating. The solar control coating is, in particular, a transparent, electrically conductive coating. A transparent coating is understood to be a coating that has an average transmission in the visible spectral range of at least 70%, thus not significantly restricting visibility through the pane. Preferably, at least 80% of the base area of ​​the composite pane is provided with the solar control coating. In particular, the solar control coating is applied over the entire surface with the exception of a peripheral edge region and optionally local areas that serve as communication, sensor, or camera windows to ensure the transmission of electromagnetic radiation through the composite pane and are therefore not provided with the solar control coating.The surrounding uncoated edge area, for example, has a width of up to 20 cm. It prevents direct contact of the solar control coating with the surrounding atmosphere, thus protecting the solar control coating inside the laminated pane from corrosion and damage.

[0017] The sun protection coating is a layer stack or a layer sequence, in particular of thin layers, comprising a plurality of electrically conductive, in particular metal-containing layers, wherein each electrically conductive layer is arranged between two dielectric layers or layer sequences. The coating is thus a thin-film stack with n electrically conductive layers and (n+1) dielectric layers or layer sequences, where n is a natural number and a lower dielectric layer or layer sequence is alternately followed by a conductive layer and a dielectric layer or layer sequence. Such coatings are known as sun protection coatings and heatable coatings, wherein the electrically conductive layers are typically silver-based.

[0018] If a first layer is arranged above a second layer, this means, within the meaning of the invention, that the first layer is arranged further away from the substrate to which the coating is applied than the second layer. If a first layer is arranged below a second layer, this means, within the meaning of the invention, that the second layer is arranged further away from the substrate than the first layer. If a first layer is arranged above or below a second layer, this does not necessarily mean, within the meaning of the invention, that the first and second layers are in direct contact with one another. One or more further layers can be arranged between the first and second layers, unless this is explicitly excluded.

[0019] The sun protection coating is preferably applied to a surface of the two panes facing the intermediate layer, i.e., the interior-facing surface of the outer pane or the exterior-facing surface of the inner pane. Alternatively, the sun protection coating can also be arranged within the thermoplastic intermediate layer, for example, applied to a carrier film arranged between two thermoplastic connecting films. It is particularly preferred if the sun protection coating is applied to the interior-facing surface of the outer pane. This achieves a particularly pronounced sun protection effect and significantly improves thermal comfort. Furthermore, in certain embodiments, it may be desirable to provide the interior-facing surface of the inner pane with a coating, for example, a reflective coating for the radiation of the imaging unit.This is easier to achieve if the solar control coating is not arranged on the opposite outer surface of the inner pane, because double-sided coating processes are very complex.

[0020] The solar protection coating according to the invention has three electrically conductive layers. The said natural number n is therefore at least 3. The coating thus comprises (at least) the following layers or layer sequences, which are arranged in the specified order starting from the substrate on which the coating is deposited (i.e., in particular, the outer pane, the inner pane, or a carrier film in the intermediate layer):

[0021] - a first dielectric layer or layer sequence,

[0022] - a first electrically conductive layer,

[0023] - a second dielectric layer or layer sequence,

[0024] - a second electrically conductive layer,

[0025] - a third dielectric layer or layer sequence,

[0026] - a third electrically conductive layer,

[0027] - a fourth dielectric layer or layer sequence.

[0028] The sun protection coating can have further electrically conductive layers and dielectric layers or layer sequences (n>3), in particular above the fourth dielectric layer or layer sequence. However, the sun protection coating preferably has exactly three electrically conductive layers and four dielectric layers or layer sequences (n=3). In a preferred embodiment, the sun protection coating consists of the aforementioned layers or layer sequences, wherein optionally further metal-containing layers can be present that do not contribute significantly to the electrical conductivity and IR-reflecting effect of the coating but serve a different purpose. This applies in particular to metallic blocker layers with geometric thicknesses of less than 1 nm, which are preferably arranged between the electrically conductive layers and the dielectric layer sequences located directly above and / or below them.

[0029] The sun protection coating according to the invention is characterized by a low reflectance against the radiation of the imaging unit, a high light transmission, and a high reflectance in the (near) IR range. The selection of the thicknesses of the electrically conductive layers is crucial for this. According to the invention, the thickness (layer thickness) is

[0030] - the first electrically conductive layer of 6 nm to 10 nm,

[0031] - the second electrically conductive layer of 6 nm to 10 nm,

[0032] - the third electrically conductive layer from 10 nm to 15 nm.

[0033] In addition, according to the invention

[0034] - the ratio of the thickness of the second electrically conductive layer to the thickness of the first electrically conductive layer is from 0.9 to 1.3,

[0035] - the ratio of the thickness of the second electrically conductive layer to the thickness of the third electrically conductive layer is from 0.5 to 1.0 and

[0036] - the ratio of the thickness of the first electrically conductive layer to the thickness of the third electrically conductive layer is from 0.5 to 1.0.

[0037] The ratio of the thickness of a first layer to the thickness of a second layer is calculated as the quotient of the thickness of the first layer divided by the thickness of the second layer. Based on the ratios according to the invention, it follows that the third electrically conductive layer is the thickest electrically conductive layer.

[0038] Unless otherwise stated, the specification of layer thicknesses refers to the geometric thickness of a layer. If the optical thickness is meant instead, this is explicitly stated. The optical thickness, as defined by the invention, is the product of the geometric thickness and the refractive index at 550 nm.

[0039] The sun protection coating in the composite pane preferably has a reflectance of less than 5% with respect to the radiation from the imaging unit. This refers to the reflectance of the sun protection coating or the surface provided with it, measured on the composite pane. The sun protection coating preferably has a reflectance of less than 5% at the wavelength of the radiation from the imaging unit, both with respect to s-polarized radiation and with respect to p-polarized radiation. A particular advantage of the sun protection coating according to the invention is that it is suitable for HUD projection arrangements and, in particular, leads to a low-pronged ghost image, regardless of whether the HUD is operated with s-polarized or p-polarized radiation.

[0040] The solar control coating always results in a ghost image, regardless of whether the projection setup is measured with s-polarized or p-polarized radiation, as explained in more detail below. The ghost image is spatially offset from the main image and can therefore be analyzed in isolation. This allows the reflectance of the solar control coating in the laminated pane to be determined, even if reflections are still occurring on other surfaces.

[0041] The reflectance of the solar control coating in the laminated pane of less than 5% (especially for both p-polarized and s-polarized radiation) is preferential not only for the radiation from the imaging unit, but also for the standard D65 light source. This allows laminated panes to be examined and characterized even without precise knowledge of the imaging unit.

[0042] The reflectance is measured as the integrated reflectance at an angle of incidence of 65°. The angle of incidence is the angle of the radiation vector to the surface normal of the interior surface of the inner pane. The laminated pane is therefore irradiated via the inner pane.

[0043] The reflection color in the LAB color space preferably has a* values ​​and b* values ​​of -10 to +10, in particular of -5 to +5 for at least one polarization direction (in particular p-polarized radiation), preferably for both polarization directions (p- and s-polarized radiation).

[0044] The laminated pane preferably has a TTS value (incident solar energy measured according to ISO 13837 with Convention A and a wind speed of 4 m / s) of less than 50%, which is particularly due to the IR-reflecting effect of the solar control coating. The specified TTS value refers in particular to a laminated pane with an outer pane and an inner pane made of clear soda-lime glass and an untinted intermediate layer (in particular formed from an untinted PVB film). The laminated pane (or its see-through area) preferably has a total transmittance (light transmittance) of greater than 70%, based on illuminant A, particularly preferably greater than 72%, and most preferably greater than 75%. These values ​​serve to characterize the transmittance of the solar control coating and refer in particular to a laminated pane that has no coating other than the solar control coating.The high transmission value of greater than 75% has the particular advantage that the sun protection coating can be combined with other coatings that further reduce light transmission. An example of such an additional coating is the reflective layer when using p-polarized radiation from the imaging unit. The term "total transmission" refers to the method for testing the light transmittance of motor vehicle windows specified in ECE-R 43, Annex 3, Section 9.1. The outside reflectance of the laminated pane is preferably less than 15%, in particular less than 13%. It is measured at an angle of incidence of 8% to the outside surface normal (normal of the outside surface of the outer pane). The light transmission and the outside reflectance are measured in particular using standard light source A and a detector aperture angle of 2° ("2° detector").

[0045] The composite pane according to the invention is also characterized by a neutral external reflection color with a low dependence on the angle of incidence. The external reflection color is typically determined using a standard D65 light source and an observation angle of 10°.

[0046] Each electrically conductive layer preferably contains at least one metal or metal alloy and is particularly preferably based on the metal or metal alloy, i.e., consists essentially of the metal or metal alloy apart from any doping or impurities. The electrically conductive layers are preferably based on silver (Ag) or a silver-containing alloy. In an advantageous embodiment, each electrically conductive layer contains at least 90% by weight silver, preferably at least 99% by weight silver, particularly preferably at least 99.9% by weight silver. The silver layers may contain doping, for example palladium, gold, copper, or aluminum. Alternatively, the electrically conductive layers may also be based on gold, copper, or aluminum, for example.

[0047] If a thin film is formed based on a material, the layer consists predominantly of this material along with any impurities or dopants. In a preferred embodiment, the thickness (layer thickness) is

[0048] - the first electrically conductive layer from 7 nm to 9 nm, in particular from 7 nm to 8 nm,

[0049] - the second electrically conductive layer from 7 nm to 10 nm, in particular from 7 nm to 9 nm,

[0050] - the third electrically conductive layer from 10 nm to 13 nm, in particular from 10 nm to 12 nm.

[0051] In a preferred embodiment,

[0052] - the ratio of the thickness of the second electrically conductive layer to the thickness of the first electrically conductive layer is from 1.0 to 1.2,

[0053] - the ratio of the thickness of the second electrically conductive layer to the thickness of the third electrically conductive layer is from 0.6 to 0.9, in particular from 0.6 to 0.8 and

[0054] - the ratio of the thickness of the first electrically conductive layer to the thickness of the third electrically conductive layer is from 0.6 to 0.9, in particular from 0.6 to 0.8.

[0055] The advantageous properties of the sun protection coating (in particular, low reflectance relative to the imaging unit with high light transmission and low TTS value) are provided in particular by the thicknesses of the electrically conductive layers according to the invention. They can be further optimized by the dielectric layers or layer sequences, with their optical thickness being particularly influential. In an advantageous embodiment,

[0056] - the first dielectric layer or layer sequence has an optical thickness of 70 nm to 100 nm, preferably of 70 nm to 90 nm, in particular of 70 nm to 80 nm;

[0057] - the second dielectric layer or layer sequence has an optical thickness of 130 nm to 200 nm, preferably of 140 nm to 160 nm, in particular of 140 nm to 150 nm;

[0058] - the third dielectric layer or layer sequence has an optical thickness of 130 nm to 200 nm, preferably 130 nm to 180 nm, in particular 130 nm to 150 nm; and

[0059] - the fourth dielectric layer or layer sequence has an optical thickness of 90 nm to 150 nm, preferably of 90 nm to 120 nm, in particular of 95 nm to 115 nm.

[0060] Preferably

[0061] - the ratio of the optical thickness of the second dielectric layer or layer sequence to the optical thickness of the first dielectric layer or layer sequence is from 1.8 to 3.0, particularly preferably from 1.9 to 2.5, in particular from 1.9 to 2.1; - the ratio of the optical thickness of the second dielectric layer or layer sequence to the optical thickness of the third dielectric layer or layer sequence is from 0.8 to 1.2, particularly preferably from 0.9 to 1.1;

[0062] - the ratio of the optical thickness of the second dielectric layer or layer sequence to the optical thickness of the fourth dielectric layer or layer sequence is from 1.2 to 3.0, particularly preferably from 1.3 to 2.0, in particular from 1.3 to 1.5;

[0063] - the ratio of the optical thickness of the first dielectric layer or layer sequence to the optical thickness of the third dielectric layer or layer sequence is from 0.3 to 0.8, particularly preferably from 0.4 to 0.6; and

[0064] - the ratio of the optical thickness of the first dielectric layer or layer sequence to the optical thickness of the fourth dielectric layer or layer sequence is from 0.5 to 1.0, particularly preferably from 0.6 to 0.8.

[0065] From the given ratios it follows that the second dielectric layer(s) is thicker than the first and fourth dielectric layer(s) and that the first dielectric layer(s) is the thinnest dielectric layer(s).

[0066] The laminated pane has a transparent see-through area that is intended for viewing. The laminated pane can also have an opaque masking area. Such masking areas are common, for example, in vehicle windows (particularly windshields and rear windows). The masking area is arranged in a circumferential edge region and surrounds the central see-through area. The masking area is typically formed by an opaque masking print on a surface of the outer pane and / or the inner pane. The masking print is made in particular from an enamel containing glass frits and a pigment, is screen-printed and then fired into the pane surface. Alternatively, opaque films can also be used in the intermediate layer.

[0067] The HUD area is preferably arranged in the see-through area of ​​the composite pane, as is the case with HLIDs in the narrower sense. Alternatively, it is also possible for the HUD area to be arranged in the masking area. Such projection arrangements are also referred to as head-up displays (HUDs in the broader sense) within the meaning of the invention. The projection arrangement can be operated with s-polarized or p-polarized radiation from the imaging unit. The sun protection coating is compatible with both, which is a major advantage of the invention. The direction of polarization refers to the plane of incidence of the radiation on the composite pane. P-polarized radiation refers to radiation whose electric field oscillates in the plane of incidence. S-polarized radiation refers to radiation whose electric field oscillates perpendicular to the plane of incidence.The plane of incidence is spanned by the incidence vector and the surface normal of the composite pane at a point within the HUD area, preferably in the geometric center of the HUD area. Due to the pane curvature common in vehicles, which affects the plane of incidence and thus the definition of polarization, the polarization components (in particular the ratio of p-polarized radiation to s-polarized radiation or vice versa) can differ from this reference point at other locations. To generate the desired polarized radiation, a polarization filter or a polarizing beam splitter, for example, can be arranged between the imaging unit and the windshield in the beam path if the imaging unit itself does not already provide radiation of the desired polarization direction.

[0068] The imaging unit is preferably a projector (HUD projector). Alternatively, the imaging unit can be a screen ("display", electronic display), in particular an LED, OLED, or LCD screen. Projectors are particularly common for HUDs in the narrower sense, in which the HUD area is arranged in the see-through area of ​​the composite pane. Screens are particularly common for HUDs in the broader sense, in which the HUD area is arranged in an opaque masking area.

[0069] The imaging unit is directed at the HUD area of ​​the composite pane. It is arranged on the interior side of the composite pane and irradiates the composite pane via the interior surface of the inner pane. When the HUD is in operation, the radiation emitted by the imaging unit irradiates the HUD area to generate the HUD projection or display image. The radiation from the imaging unit lies in the visible spectral range of the electromagnetic spectrum, in particular in the spectral range from 450 nm to 650 nm – typical imaging units operate at wavelengths of 473 nm, 550 nm, and 630 nm (RGB). The angle of incidence of the radiation onto the composite pane is preferably between 45° and 70°, particularly preferably between 60° and 70°, for example, approximately 65°. These angles of incidence deviate only slightly from the Brewster angle.The Brewster angle for an air-glass transition in the case of soda-lime glass, which is generally used for window panes, is 57.2° (with a refractive index of soda-lime glass of 1.55 at a wavelength of 550 nm). The angle of incidence can also be referred to as the angle of incidence. It is the angle between the incidence vector of the radiation and the interior-side surface normal (i.e. the surface normal to the interior-side surface of the inner pane) determined at a point in the display area, preferably in the geometric center of the display area. If the angle of incidence corresponds exactly to the Brewster angle, only s-polarized radiation is reflected, not p-polarized radiation. In an advantageous embodiment, the angle of incidence deviates from the Brewster angle by a maximum of 10°.

[0070] In one embodiment of the projection arrangement according to the invention, the imaging unit is operated with s-polarized radiation. This means that the radiation from the imaging unit is predominantly s-polarized, i.e., has a proportion of s-polarized radiation of more than 50%, preferably at least 80%. The radiation from the imaging unit is preferably completely or almost completely s-polarized (essentially purely s-polarized). The s-polarized radiation proportion is 100% or deviates only insignificantly therefrom. The proportion of s-polarized radiation is determined at the point in the HUD area where the largest proportion of s-polarized radiation occurs. The projection arrangement is preferably designed such that this point is located in the geometric center of the HUD area.

[0071] S-polarized radiation is significantly reflected by the external surfaces of the laminated glass, i.e., the interior surface of the inner glass and the exterior surface of the outer glass. The interlayer typically has a refractive index that differs only slightly from that of the outer and inner glass, so that the interior surface of the outer glass and the exterior surface of the inner glass do not represent reflective interfaces. This double reflection essentially creates two HUD projections: the main image and a slightly offset ghost image. This is distracting for the user.To eliminate or at least reduce this problem, the outer surface of the outer pane and the interior surface of the inner pane are preferably arranged at an angle to one another, which is selected such that the main image and the ghost image are superimposed on one another or at least their distance from one another is reduced. The distance between said surfaces increases in a vertical progression "from bottom to top," i.e., in a direction from the lower edge to the upper edge, at least in the HUD area. This is preferably achieved by a wedge-shaped intermediate layer, alternatively or additionally by a wedge-shaped outer pane and / or inner pane.

[0072] The intermediate layer is preferably wedge-shaped, so that its thickness increases in a direction from the lower edge to the upper edge of the composite pane. This increase in thickness is present at least in the HUD region, but typically along the entire length between the lower edge and the upper edge. The angle between the two surfaces of the intermediate layer is referred to as the wedge angle. The wedge angle can be constant or vary along the vertical axis. If the wedge angle is not constant, the tangents to the surfaces must be used to measure it at a point. Typical wedge angles are in the range from 0.2 mrad to 1 mrad, preferably from 0.3 mrad to 0.7 mrad, particularly preferably from 0.4 mrad to 0.5 mrad.

[0073] The wedge-shaped intermediate layer is created, in particular, by using a so-called wedge film (a film with increasing thickness in one direction) to form the intermediate layer. A wedge film can be produced by suitable extrusion of the film or by stretching a film with a constant thickness in its initial state.

[0074] The composite pane can optionally be provided with an additional reflective layer to increase the reflectivity against s-polarized radiation.

[0075] In a further embodiment of the projection arrangement according to the invention, the imaging unit is operated with p-polarized radiation. This means that the radiation from the imaging unit is predominantly p-polarized, i.e., has a proportion of p-polarized radiation of more than 50%, preferably at least 80%. The radiation from the imaging unit is preferably completely or almost completely p-polarized (essentially purely p-polarized). The p-polarized radiation proportion is 100% or deviates only insignificantly therefrom. The proportion of p-polarized radiation is determined at the point in the HUD area where the largest proportion of p-polarized radiation occurs. The projection arrangement is preferably designed such that this point is located in the geometric center of the HUD area.

[0076] Since the angle of incidence typically does not deviate significantly from the Brewster angle, p-polarized radiation is not reflected, or only slightly reflected, by the external surfaces of the laminated pane. Therefore, it is not necessary to arrange these surfaces at an angle to each other, as is common with s-polarized radiation. Instead, the laminated pane and its components (outer pane, inner pane, intermediate layer) preferably have a constant thickness. The outer surface of the outer pane and the interior surface of the inner pane are preferably aligned parallel to each other.

[0077] The composite pane is provided with a reflective layer suitable for reflecting p-polarized radiation. The reflective layer is particularly intended to reflect the p-polarized radiation of the imaging unit to generate a display image. The reflective layer preferably has an average reflectance of at least 5%, particularly preferably at least 10%, relative to p-polarized radiation in the spectral range from 450 nm to 650 nm.

[0078] The reflective layer covers at least the HUD area of ​​the composite pane, but can also extend beyond it. It is preferably positioned on the interior side of the sun protection coating, thus being closer to the imaging unit than the sun protection coating, so that the radiation from the imaging unit first hits the reflective layer and only then the sun protection coating. The reflective layer can

[0079] - be arranged as a reflective film within the intermediate layer; the sun protection coating is then preferably arranged on the interior-side surface of the outer pane or also in the intermediate layer at a shorter distance from the outer pane;

[0080] - be arranged on the outside surface of the inner pane; the solar protection coating is then preferably arranged on the inside surface of the outer pane or within the intermediate layer;

[0081] - be arranged on the interior surface of the inner pane; the solar protection coating is then preferably arranged on the interior surface of the outer pane, within the intermediate layer or on the exterior surface of the inner pane.

[0082] Since there is only a single reflective surface (namely the reflective layer), no ghosting occurs with such a projection setup. In addition, the use of p-polarized radiation also has the advantage that the HUD image is visible to wearers of polarization-selective sunglasses, which typically only allow p-polarized radiation to pass through and block s-polarized radiation. Furthermore, the use of relatively expensive wedge films can be dispensed with. The reflective layer can be designed in various ways. In particular, the following reflective layer designs are preferred:

[0083] - a thin-film coating with at least one metal-containing layer, in particular a silver layer, between dielectric layers or layer sequences; due to the susceptibility of the metallic layer to corrosion, such a coating must be arranged on the interior surface of the outer pane, the exterior surface of the inner pane or as a reflective film (coating applied to a carrier film) within the intermediate layer;

[0084] - a purely dielectric thin-film coating comprising alternating dielectric layers with a high and a low refractive index, wherein the desired reflection properties are caused by optical interference effects, which can be adjusted by the choice of materials (or refractive indices) and layer thicknesses; such a coating can be positioned in the same way as the metal-containing thin-film coating described above, also on the interior surface of the inner pane, since the dielectric coating is typically not susceptible to corrosion;

[0085] - a purely dielectric reflective film which is designed as a polymeric film having alternating individual layers with a high and a low refractive index; here too, the desired reflective properties are achieved through optical interference effects; at least one of the two layer types is preferably based on PET; the other layer type can also be based on PET, with the different refractive indices being achieved by suitable additives, based on a PET copolymer or based on another polymer, for example PMMA; such a reflective film can also be embedded in the intermediate layer, positioned between the intermediate layer and the inner pane, or attached, for example glued, to the interior-side surface of the inner pane.

[0086] It is particularly preferred that the reflective layer be formed as a purely dielectric thin-film coating on the interior-side surface of the inner pane. This achieves a particularly clear display image.

[0087] The reflective layer is preferably partially transparent and partially reflective. If the HUD area is located in the see-through area (HUD in the narrow sense), partial transparency is required to ensure visibility. If the HUD area is located in an opaque masking area (HUD in the broad sense), a full mirror could in principle also be used as the reflective layer. However, since no reflection occurs on the sun protection coating anyway (at least if the reflective layer is located on the interior side of the sun protection coating) and no ghost image, the reflective properties of the sun protection coating are irrelevant.

[0088] In addition to the electrically conductive layers, the dielectric layers or layer sequences influence the properties of the solar protection coating, in particular its material or refractive index and its layer thickness. In a preferred embodiment, only dielectric layer sequences are present, so that between adjacent conductive layers, as well as above the uppermost conductive layer and below the lowermost conductive layer, dielectric layer sequences consisting of a plurality of dielectric layers are present, rather than individual dielectric layers.

[0089] In a preferred embodiment of the invention, all dielectric layers present have a refractive index greater than 1.8, preferably greater than 1.9. In other words, all dielectric layers or layer sequences are formed exclusively from dielectric layers with a refractive index greater than 1.8. This achieves good results. The dielectric layers can, for example, be based on silicon nitride, silicon-metal mixed nitrides (such as silicon zirconium nitride (SiZrN), silicon-aluminum mixed nitride, silicon-hafnium mixed nitride or silicon-titanium mixed nitride), aluminum nitride (AlN), tin oxide (SnO), manganese oxide (MnO), tungsten oxide (WO3), niobium oxide (Nb205), bismuth oxide (Bi203), titanium oxide (TiCh), zinc oxide (ZnO) or tin-zinc mixed oxide (SnZnO).

[0090] The materials may contain dopants, particularly aluminum, boron, antimony, zirconium, or titanium. These dopants can provide dielectric materials with a certain degree of electrical conductivity. However, those skilled in the art will identify them as dielectric layers in terms of their function, as is common in the field of thin films. The material of the dielectric layers preferably has an electrical conductivity (the inverse of the resistivity) of less than 10' 4 S / m. The material of the electrically conductive layers preferably has an electrical conductivity of greater than 10 4 S / m. The oxides and nitrides mentioned in this description can be deposited stoichiometrically, substoichiometrically, or superstoichiometrically with respect to oxygen or nitrogen content.

[0091] In the context of the present invention, the refractive index is given relative to a wavelength of 550 nm, unless explicitly stated otherwise. The refractive index is fundamentally independent of the measurement method. It can be determined, for example, using ellipsometry. Ellipsometers are commercially available, for example, from Sentech.

[0092] In an advantageous embodiment, each dielectric layer or layer sequence contains an anti-reflective coating. The anti-reflective coatings reduce the reflection of visible light and thus increase the transparency of the coated pane. The anti-reflective coatings are formed, for example, from silicon nitride (SiN), silicon-metal mixed nitrides such as silicon zirconium nitride (SiZrN), aluminum nitride (AlN), or tin oxide (SnO). The anti-reflective coatings can also contain doping. The anti-reflective coatings preferably have thicknesses of 10 nm to 100 nm, particularly preferably of 10 nm to 50 nm.

[0093] The anti-reflective coatings can in turn be divided into at least two sublayers, in particular into at least one dielectric layer with a refractive index of less than 2.1 and at least one optically highly refractive layer with a refractive index of greater than or equal to 2.1. Preferably, at least one anti-reflective coating arranged between two electrically conductive layers is divided in this way, particularly preferably all anti-reflective layers arranged between two electrically conductive layers, and most particularly preferably all anti-reflective layers. The subdivision of the anti-reflective coating leads to a lower sheet resistance of the electrically conductive coating while simultaneously achieving high transmission and high color neutrality. The order of the sublayers can, in principle, be chosen arbitrarily.The thickness of the optically highly refractive layer is preferably from 10% to 99%, particularly preferably from 30% to 90% of the total thickness of the anti-reflective layer.

[0094] The optically high-index layer with a refractive index greater than or equal to 2.1 contains, for example, MnO, WO3, Nb2O5, Bi2O3, TiO2, ZrSn4, and / or AlN, preferably a silicon-metal mixed nitride, for example, silicon-hafnium mixed nitride or silicon-titanium mixed nitride, particularly preferably silicon-zirconium mixed nitride (SiZrN). This is particularly advantageous with regard to the sheet resistance of the electrically conductive coating. The silicon-zirconium mixed nitride preferably contains dopants, for example, aluminum. The proportion of zirconium (Zr) is preferably between 5 and 45 wt.%, particularly preferably between 10 and 30 wt.%. The refractive index of the optically high-index layer depends significantly on the Zr content.

[0095] The dielectric layer with a refractive index of less than 2.1 preferably has a refractive index between 1.6 and 2.1, particularly preferably between 1.9 and 2.1. The dielectric layer preferably contains at least one oxide, for example tin oxide, and / or a nitride, particularly preferably silicon nitride. The silicon nitride preferably has dopants, for example aluminum.

[0096] In an advantageous embodiment, one or more dielectric layer sequences comprise a first matching layer, preferably each dielectric layer sequence arranged beneath an electrically conductive layer. The first matching layer is preferably arranged above the anti-reflective layer. The first matching layer is preferably arranged directly beneath the electrically conductive layer, so that it has direct contact with the conductive layer. This is particularly advantageous with regard to the crystallinity of the electrically conductive layer.

[0097] In an advantageous embodiment, one or more dielectric layer sequences have a smoothing layer, preferably each dielectric layer sequence arranged between two electrically conductive layers, particularly preferably additionally the bottommost dielectric layer sequence (first dielectric layer sequence). The smoothing layer is arranged below one of the first adaptation layers, preferably between the anti-reflective layer and the first adaptation layer, if such a first adaptation layer is present. The smoothing layer is particularly preferably in direct contact with the first adaptation layer. The smoothing layer optimizes, in particular smoothes, the surface for an electrically conductive layer subsequently applied above. An electrically conductive layer deposited on a smoother surface has a higher transmittance and, at the same time, a lower sheet resistance.The layer thickness of a smoothing layer is preferably from 5 nm to 20 nm, particularly preferably from 7 nm to 12 nm. The smoothing layer preferably has a refractive index of less than 2.2. The smoothing layer preferably contains at least one non-crystalline oxide. The oxide can be amorphous or partially amorphous (and thus partially crystalline), but is not completely crystalline. The non-crystalline smoothing layer has low roughness and thus forms an advantageously smooth surface for the layers to be applied above the smoothing layer. The non-crystalline smoothing layer further effects an improved surface structure of the layer deposited directly above the smoothing layer, which is preferably the first adaptation layer. The smoothing layer can, for example, contain at least one oxide of one or more of the elements tin, silicon, titanium, zirconium, hafnium, zinc, gallium, and indium.The smoothing layer particularly preferably contains a non-crystalline mixed oxide. The smoothing layer very particularly preferably contains a tin-zinc mixed oxide (ZnSnO). The mixed oxide preferably contains dopants, for example, antimony. The smoothing layer can, for example, contain an antimony-doped tin-zinc mixed oxide. The mixed oxide preferably has a substoichiometric oxygen content. The tin content is preferably between 10 and 40 wt.%, particularly preferably between 12 and 35 wt.%.

[0098] In an advantageous embodiment, one or more dielectric layer sequences comprise a second matching layer, preferably each dielectric layer sequence arranged above an electrically conductive layer. The second matching layer is preferably arranged below the anti-reflective layer.

[0099] The first and second adaptation layers improve the surface resistance of the coating. The first adaptation layer and / or the second adaptation layer preferably contains zinc oxide ZnOi-δ where 0 < δ < 0.01. The first adaptation layer and / or the second adaptation layer further preferably contains dopants, for example aluminum. The zinc oxide is preferably deposited substoichiometrically with respect to oxygen in order to avoid a reaction of excess oxygen with the silver-containing layer. The layer thicknesses of the first adaptation layer and the second adaptation layer are preferably from 5 nm to 20 nm, particularly preferably from 10 nm to 20 nm, in particular from 10 nm to 15 nm.

[0100] In an advantageous embodiment, the electrically conductive coating comprises one or more blocker layers. Preferably, at least one blocker layer is assigned to at least one, particularly preferably each, electrically conductive layer. The blocker layer is in direct contact with the electrically conductive layer and is arranged directly above or directly below the electrically conductive layer. Therefore, no further layer is arranged between the electrically conductive layer and the blocker layer. A blocker layer can also be arranged directly above and directly below a conductive layer. The blocker layer preferably contains niobium, titanium, nickel, chromium and / or alloys thereof, particularly preferably nickel-chromium alloys. The layer thickness of the blocker layer is preferably from 0.1 nm to 1 nm, particularly preferably from 0.1 nm to 0.5 nm.A blocker layer directly beneath the electrically conductive layer serves in particular to stabilize the electrically conductive layer during heat treatment and improves the optical quality of the electrically conductive coating. A blocker layer directly above the electrically conductive layer prevents contact of the sensitive electrically conductive layer with the oxidizing reactive atmosphere during the deposition of the subsequent layer by reactive sputtering, for example, the second matching layer.

[0101] In an advantageous embodiment, a dielectric layer sequence is arranged between each two electrically conductive layers, which comprises:

[0102] - an anti-reflective coating based on silicon nitride, silicon-metal mixed nitride such as silicon zirconium nitride, aluminum nitride and / or tin oxide,

[0103] - a smoothing layer based on an oxide of one or more of the elements tin, silicon, titanium, zirconium, hafnium, zinc, gallium and indium,

[0104] - a first and a second adaptation layer based on zinc oxide and

[0105] - Optionally, a blocking layer based on niobium, titanium, nickel, chromium, and / or alloys thereof. A specific order of the layers is not required. Below the lowest conductive layer and above the uppermost conductive layer, an anti-reflective coating and an adaptation layer based on the aforementioned preferred materials are preferably arranged. Below the lowest conductive layer, a smoothing layer based on the aforementioned preferred materials is preferably additionally arranged.

[0106] In a particularly preferred embodiment, the sun protection coating comprises, starting from the substrate to which it is applied:

[0107] - a first dielectric layer sequence, comprising: o an anti-reflection layer, preferably with a thickness of 13 nm to 18 nm, in particular from 14 nm to 16 nm, o a smoothing layer, preferably with a thickness of 7 nm to 12 nm, in particular from 8 nm to 10 nm, o a first adaptation layer, preferably with a thickness of 10 nm to 15 nm, in particular from 11 nm to 13 nm,

[0108] - a first electrically conductive layer with a thickness of 6 nm to 10 nm, preferably 7 nm to 9 nm,

[0109] - preferably a first blocking layer, preferably with a thickness of 0.1 nm to 0.5 nm,

[0110] - a second dielectric layer sequence, comprising: o a second adaptation layer, preferably with a thickness of 12 nm to 17 nm, in particular from 14 nm to 16 nm, o an anti-reflection layer, preferably with a thickness of 27 nm to 32 nm, in particular from 28.5 nm to 30.5 nm, o a smoothing layer, preferably with a thickness of 10 nm to 15 nm, in particular from 10.5 nm to 12.5 nm, o a first adaptation layer, preferably with a thickness of 12 nm to 17 nm, in particular from 14 nm to 16 nm,

[0111] - a second electrically conductive layer with a thickness of 6 nm to 10 nm, preferably 7 nm to 10 nm, in particular 7 nm to 9 nm,

[0112] - preferably a second blocking layer, preferably with a thickness of 0.1 nm to 0.5 nm,

[0113] - a third dielectric layer sequence, comprising: o a second adaptation layer, preferably with a thickness of 12 nm to 17 nm, in particular from 13 nm to 15 nm, o an anti-reflection layer, preferably with a thickness of 30 nm to 37 nm, in particular from 30.5 nm to 32.5 nm, o a smoothing layer, preferably with a thickness of 10 nm to 15 nm, in particular from 7 nm to 9 nm, o a first adaptation layer, preferably with a thickness of 12 nm to 17 nm, in particular from 13 nm to 15 nm,

[0114] - a third electrically conductive layer with a thickness of 10 nm to 15 nm, preferably 10 nm to 12 nm,

[0115] - preferably a third blocking layer, preferably with a thickness of 0.1 nm to 0.5 nm,

[0116] - a fourth dielectric layer sequence, comprising: o a second adaptation layer, preferably with a thickness of 12 nm to 17 nm, in particular from 13 nm to 15 nm, o an anti-reflective layer, preferably with a thickness of 32 nm to 38 nm. The sun protection coating very particularly preferably consists of the layers mentioned, wherein further blocking layers with a preferred thickness of 0.1 nm to 0.5 nm can optionally be present directly beneath the electrically conductive layers.

[0117] The electrically conductive layers are preferably based on silver, the adaptation layers are preferably based on zinc oxide, the smoothing layers are preferably based on tin-zinc mixed oxide, and the blocking layers are preferably based on a nickel-chromium alloy.

[0118] The anti-reflective coatings are preferably based on silicon nitride and / or silicon-metal mixed nitride (in particular silicon zirconium nitride). Particularly preferably, at least one, in particular all, anti-reflective coatings are divided into at least one dielectric layer with a refractive index of less than 2.1, in particular based on silicon nitride, and at least one optically high-index layer with a refractive index greater than or equal to 2.1, in particular based on metal mixed nitride (preferably silicon zirconium nitride). The refractive index of such a layer can be adjusted by the zirconium content.

[0119] The individual anti-reflective coatings particularly preferably comprise the following individual layers, in the specified order starting from the substrate:

[0120] - first anti-reflection layer: o a dielectric layer with a refractive index of less than 2.1, preferably with a thickness of 8 nm to 11 nm, o an optically highly refractive layer with a refractive index of 2.1 to 2.3, preferably with a thickness of 5 nm to 8 nm,

[0121] - second anti-reflective layer: o an optically high-refractive index layer with a refractive index of 2.1 to 2.3, preferably with a thickness of 4 nm to 7 nm, o an optically high-refractive index layer with a refractive index of 2.3 to 2.5, preferably with a thickness of 4 nm to 8 nm, in particular 5 nm to 7 nm, o a dielectric layer with a refractive index of less than 2.1, preferably with a thickness of 9 nm to 14 nm, in particular 10 nm to 14 nm, o an optically high-refractive index layer with a refractive index of 2.1 to 2.3, preferably with a thickness of 4 nm to 7 nm,

[0122] - third anti-reflective layer: o a dielectric layer with a refractive index of less than 2.1, preferably with a thickness of 4 nm to 11 nm, in particular 4 nm to 7 nm, o an optically highly refractive layer with a refractive index of 2.1 to 2.3, preferably with a thickness of 25 nm to 29 nm,

[0123] - fourth anti-reflective layer: o an optically highly refractive layer with a refractive index of 2.1 to 2.3, preferably with a thickness of 23 nm to 29 nm, in particular of 26 nm to 29 nm, o a dielectric layer with a refractive index of less than 2.1, preferably with a thickness of 5 nm to 10 nm.

[0124] The outer pane and the inner pane are preferably made of glass, in particular soda-lime glass, which is common for window panes. However, the panes can also be made of other types of glass (e.g., borosilicate glass, quartz glass, aluminosilicate glass) or transparent plastics (e.g., polymethyl methacrylate or polycarbonate). The thickness of the outer pane and the inner pane can vary widely. Preferably, panes with a thickness in the range of 0.8 mm to 5 mm, more preferably 1.4 mm to 2.9 mm, for example, with the standard thicknesses of 1.6 mm or 2.1 mm, are used.

[0125] The outer pane, the inner pane, and the thermoplastic interlayer can be clear and colorless, but also tinted or colored. The outer pane and the inner panes can independently be non-tempered, semi-tempered, or thermally or chemically toughened.

[0126] The composite pane is preferably curved in one or more directions, as is common for automotive windows, with typical radii of curvature ranging from approximately 10 cm to approximately 40 m. However, the composite pane can also be flat, for example, if it is intended for use as a pane for buses, trains, or tractors.

[0127] The thermoplastic intermediate layer contains at least one thermoplastic polymer, preferably polyvinyl butyral (PVB), ethylene vinyl acetate (EVA) or polyurethane (PU) or mixtures or copolymers or derivatives thereof, particularly preferably PVB. The intermediate layer is typically formed from at least one thermoplastic film (connecting film), preferably based on one of the said polymers, in particular based on PVB. The thickness of the intermediate layer is preferably from 0.2 mm to 2 mm, particularly preferably from 0.5 mm to 1 mm. In certain embodiments, the intermediate layer can have, in addition to the at least one connecting film, a carrier film on which, for example, the sun protection coating or a reflective layer for the HUD radiation is deposited. Such a carrier film is preferably based on PET and has a thickness of 20 μm to 200 μm, in particular from 50 μm to 100 μm.

[0128] If a polymeric film or layer is formed on the basis of a material, this means in the sense of the invention that the film or layer predominantly contains the said material (proportion of greater than 50 wt.%) and can optionally contain further components, for example plasticizers, stabilizers, UV or IR absorbers.

[0129] The composite pane can be manufactured using conventional processes. The outer pane and the inner pane are laminated together via the intermediate layer, for example, using autoclave processes, vacuum bag processes, vacuum ring processes, calender processes, vacuum laminators, or combinations thereof. The bonding of the outer pane and inner pane is typically achieved using heat, vacuum, and / or pressure.

[0130] The solar control coating is preferably applied to the inner pane by physical vapor deposition (PVD), particularly preferably by cathode sputtering, and most preferably by magnetic field-assisted cathode sputtering (magnetron sputtering). In principle, however, the coating can also be applied, for example, by chemical vapor deposition (CVD), such as plasma-enhanced chemical vapor deposition (PECVD), by vapor deposition, or by atomic layer deposition (ALD). The coating is preferably deposited onto the pane in question prior to lamination. Instead of applying the electrically conductive coating to a pane surface, it can also be provided on a carrier film that is arranged in the intermediate layer, in particular, inserted between two bonding films.

[0131] If the composite pane has a reflective layer to reflect the HUD radiation, and this reflective layer is a thin-film coating, it is preferably deposited using one of the methods described above in connection with the sun protection coating, in particular by magnetic field-assisted cathode sputtering. The deposition takes place in particular on one of the surfaces of the inner pane or on a carrier film, which is inserted into the intermediate layer before lamination, in particular between two bonding films. A purely dielectric reflective film is also preferably inserted into the intermediate layer before lamination, in particular between two bonding films.

[0132] If the laminated pane is to be curved, the outer and inner panes are subjected to a bending process, preferably before lamination and preferably after any coating processes. The outer and inner panes are preferably bent congruently together (i.e., simultaneously and using the same tool), as this ensures that the shape of the panes is optimally matched for subsequent lamination. Typical temperatures for glass bending processes are, for example, 500°C to 700°C. This temperature treatment also increases transparency and reduces the sheet resistance of the conductive coating. All standard bending methods can be used, for example, gravity bending, press bending, and / or suction bending.

[0133] The invention further encompasses the use of a composite pane constructed according to the invention as a projection surface of a projection arrangement for a head-up display, with a projector directed onto the HUD area. The preferred embodiments described above apply accordingly to this use.

[0134] The invention further comprises the use of a projection arrangement according to the invention as a HUD in a vehicle on land, on water or in the air, preferably a motor vehicle, rail vehicle, aircraft or ship, in particular a passenger car or truck.

[0135] The invention is explained in more detail below with reference to a drawing and exemplary embodiments. The drawing is a schematic representation and not to scale. The drawing does not limit the invention in any way.

[0136] They show:

[0137] Fig. 1 is a plan view of a composite pane of a generic projection arrangement,

[0138] Fig. 2 shows a cross-section through a generic projection arrangement,

[0139] Fig. 3 shows a cross section through the composite pane of an embodiment of the projection arrangement according to the invention,

[0140] Fig. 4 shows a cross section through the composite pane of a further embodiment of the projection arrangement according to the invention,

[0141] Fig. 5 shows a cross section through a sun protection coating according to the invention.

[0142] Figures 1 and 2 each show a detail of a generic projection arrangement for a HUD. The projection arrangement comprises a composite pane 10, in particular the windshield of a passenger car. The projection arrangement also comprises an imaging unit 4, in particular a projector, which is directed onto an area B of the composite pane 10. In area B, which is usually referred to as the HUD area, the imaging unit 4 can generate images which are perceived by an observer 5 (vehicle driver) as virtual images on the side of the composite pane 10 facing away from them when their eyes are located within the so-called eyebox E.

[0143] The composite pane 10 is constructed of an outer pane 1 and an inner pane 2, which are bonded together by a thermoplastic intermediate layer 3. Its lower edge U is positioned downwards toward the engine of the passenger car, while its upper edge O is positioned upwards toward the roof. In the installed position, the outer pane 1 faces the outside environment, while the inner pane 2 faces the vehicle interior.

[0144] Figure 3 shows an embodiment of a composite pane 10 designed according to the invention. The outer pane 1 has an outer surface I which, in the installed position, faces the outside environment, and an inner surface II which, in the installed position, faces the interior space. Likewise, the inner pane 2 has an outer surface III which, in the installed position, faces the outside environment, and an inner surface IV which, in the installed position, faces the interior space. The outer pane 1 and the inner pane 2 are made, for example, of soda-lime glass. The outer pane 1 has, for example, a thickness of 2.1 mm, and the inner pane 2 has a thickness of 1.6 mm. The intermediate layer 3 is formed, for example, from a PVB film with a thickness of 0.76 mm. The PVB film has a substantially constant thickness, apart from any surface roughness customary in the field.

[0145] The composite pane 10 is suitable for a HUD projection arrangement with p-polarized radiation. The radiation from the imaging unit 4 is p-polarized, in particular, essentially purely p-polarized. Since the imaging unit 4 typically irradiates the composite pane 10 at an angle of incidence of approximately 65°, which is close to the Brewster angle, the radiation from the imaging unit 4 is only insignificantly reflected from the external surfaces I, IV of the composite pane 10.

[0146] To generate the display image or HUD image, the composite pane 10 is equipped with a reflective layer 30. In the embodiment shown, the reflective layer 30 is a purely dielectric thin-film coating that is not susceptible to corrosion and can therefore be arranged on the exposed interior-side surface IV of the inner pane 2. The reflective layer 30 is optimized for the reflection of p-polarized radiation. It serves as a reflective surface for the radiation from the imaging unit 4 for generating the HUD projection. The reflectance of the reflective layer 30 compared to the radiation from the imaging unit 4 is, for example, approximately 10%. Alternatively, a thin-film coating with at least one silver layer could be used as the reflective layer 30, which can be arranged, for example, on the outer surface III of the inner pane 2, where it is protected against corrosion.

[0147] The interior-side surface II of the outer pane 1 is provided with the sun protection layer 20 according to the invention. The sun protection layer 20 is intended to reflect infrared components of the sun's radiation and thereby improve thermal comfort in the vehicle interior. However, it represents a further reflective interface for the radiation from the imaging unit 4, resulting in a further HUD projection that appears offset from the HUD projection attributable to the reflective layer 30. This disruptive effect is also referred to as a ghost image. The sun protection layer 20 according to the invention has an advantageously low reflectance compared to the p-polarized radiation from the imaging unit. The ghost image is therefore not very intense and is hardly noticeable to the viewer 5. The HUD projection is therefore hardly disrupted by the sun protection layer 20.The reflective color is also neutral, so no color cast is created. The sun protection layer 20 also exhibits high light transmission, so that the transparency of the laminated pane 10 is not significantly reduced, and a good IR-reflecting effect. Furthermore, the sun protection layer 20 is characterized by low external reflection and a neutral to slightly bluish external reflection color.

[0148] Figure 4 shows an embodiment of a further composite pane 10 designed according to the invention. The outer pane 1 and the inner pane 2 are designed in the same way as in the embodiment of Figure 3. Likewise, the interior-side surface II is provided with the sun protection coating 20.

[0149] In contrast to the embodiment of Figure 3, the composite pane 10 is not provided with a reflective layer 30 intended to reflect the radiation from the imaging unit 4. The composite pane 10 is suitable for a HUD projection arrangement with s-polarized radiation. The radiation from the imaging unit 4 is s-polarized, in particular essentially purely s-polarized. It is reflected at the external surfaces of the composite pane 10, i.e., at the interior-side surface IV of the inner pane 2 and at the exterior surface I of the outer pane 1. The surfaces II, III facing the intermediate layer 3, in contrast, do not represent reflective interfaces due to the small difference between the refractive indices of soda-lime glass and PVB.

[0150] The double reflection at the external surfaces I, IV essentially results in the generation of two HUD projections or display images. If the two external surfaces I, IV are arranged parallel, these two display images appear offset to the viewer 5. In other words, the viewer 5 sees a further, offset display image in addition to the main display image, which is also commonly referred to as a ghost image.

[0151] To avoid ghosting, the intermediate layer 3 is wedge-shaped, so that its thickness increases from bottom to top, i.e., in a direction from the lower edge U to the upper edge O. This overlaps the two projections or at least reduces their distance from each other. The ghosting is then not noticeable, or at least less disruptive. The wedge-shaped intermediate layer 3 can be formed from a PVB wedge film. Such wedge films can be produced by extrusion and purchased from film manufacturers. Alternatively, it is also possible to stretch a standard film of constant thickness into the wedge shape.

[0152] The sun protection coating 20 according to the invention is compatible with both HUD projection arrangements with p-polarized radiation and with HUD projection arrangements with s-polarized radiation. Thus, the same sun protection coating 20 can be used for both applications in Figures 3 and 4. The sun protection coating 20 essentially represents a further reflective interface with respect to the radiation from the imaging unit 4. With a sufficiently high reflectivity, this would lead to a (further) ghost image. The sun protection coating 20 according to the invention is characterized in particular by a low degree of reflection with respect to the radiation from the imaging unit 4. As a result, the ghost image is very weak in intensity and is not noticeable to the viewer 5, or at least not disturbingly so.

[0153] The arrangement of the sun protection coating 20 is not limited to the interior-side surface II of the outer pane 1, as shown in the figures. In both embodiments, the sun protection coating 20 could also be arranged on the exterior surface III of the inner pane 2 or on a carrier film embedded in the intermediate layer 3.

[0154] Figure 5 shows the layer sequence of an inventive embodiment of the sun protection coating 20 on the outer pane 1. The sun protection coating 20 comprises four dielectric layer sequences M1, M2, M3, M4 and three electrically conductive layers 21.1, 21.2, 21.3, which are arranged alternately. A thin blocking layer 26.1, 26.2, 26.3 is arranged between each electrically conductive layer 21.1, 21.2, 21.3 and the overlying dielectric layer sequence M1, M2, M3, M4.

[0155] The first dielectric layer sequence M1 is composed of an anti-reflection layer 22.1, a smoothing layer 23.1, and a first matching layer 24.1. The second dielectric layer sequence M2 is composed of a second matching layer 25.2, an anti-reflection layer 22.2, a smoothing layer 23.2, and a first matching layer 24.2.

[0156] The third dielectric layer sequence M3 is composed of a second adaptation layer 25.3, an anti-reflection layer 22.3, a smoothing layer 23.3 and a first adaptation layer 24.3.

[0157] The fourth dielectric layer sequence M4 is composed of a second adaptation layer 25.4 and an anti-reflection layer 22.4.

[0158] The anti-reflective coatings 22.1, 22.2, 22.3, and 22.4 are each divided into several individual layers. The first anti-reflective coating 22.1, the third anti-reflective coating 22.3, and the fourth anti-reflective coating 22.4 are each divided into two individual layers, namely a dielectric layer 22a.1, 22a.3, 22a.4 with a refractive index of less than 2.1 and an optically highly refractive layer 22b.1, 22b.3, 22b.4 with a refractive index of greater than 2.1. The second anti-reflection layer 22.2 is divided into an optically high-refractive layer 22b.2 with a refractive index greater than 2.1, an optically high-refractive layer 22c.2 with a refractive index greater than 2.3, a dielectric layer 22a.2 with a refractive index less than 2.1 and a further optically high-refractive layer 22d.2 with a refractive index greater than 2.1.

[0159] The layer sequence is shown schematically in the figure. The layer sequence of a composite pane 10 with the solar protection coating 20 on the interior-facing surface II of the outer pane 2 is shown in Table 1, together with the materials and layer thicknesses of the individual layers, for five examples 1 to 5 according to the invention.

[0160] In contrast, Table 2 shows the layer sequences of a non-inventive sun protection coating 20 (comparative example). Table 1 Table 2

[0161] The comparative example basically has a similar layer sequence as examples 1 to 5, with the anti-reflection layers 22.1, 22.2, 22.3, 22.4, the smoothing layer 23.1, 23.2, 23.3, the first adjustment layer 24.1, 24.2, 24.3, the second adjustment layer

[0162] 25.2, 25.3, 25.4, the blocking layers 26.1, 26.2, 26.3 and the electrically conductive layers 21.1, 21.2, 21.3.

[0163] The electrically conductive layers 21.1, 21.2, 21.3 are based on silver (Ag), the blocking layers 26.1, 26.2, 26.3 are based on a nickel-chromium alloy (NiCr), the smoothing layer 23.1, 23.2, 23.3 are based on tin-zinc mixed oxide (SnZnO), the first matching layers 24.1, 24.2, 24.3 and the second matching layers 25.2, 25.3, 25.4 are based on zinc oxide (ZnO), the dielectric layers 22a.1, 22a.2, 22a.3, 22a.4 with a refractive index of less than 2.1 are based on silicon nitride (SiN), the optically high-refractive layers 22b.1, 22b.2, 22b.3, 22b.4, 22d.2 with a refractive index greater than 2.1 based on a silicon-zirconium mixed nitride deposited in a nitrogen atmosphere with argon addition with a silicon-zirconium target with a zirconium content of 17 wt.% (SiZr17N) and the optically highly refractive layer 22c.2 with a refractive index greater than 2.3 based on a silicon-zirconium mixed nitride, which was deposited in a nitrogen atmosphere with added argon using a silicon-zirconium target with a zirconium content of 27 wt.% (SiZr27N). The oxides and nitrides can be deposited stoichiometrically, substoichiometrically, or superstoichiometrically with regard to the oxygen or nitrogen content, which is why a stoichiometric molecular formula was omitted. In the examples and the comparative example, however, the same stoichiometric ratio was chosen for layers based on the same material. The layers can also contain dopants and impurities. The doping for layers based on the same material was also the same in the examples and the comparative example. For example, layers based on SnZnO can be doped with antimony, and layers based on ZnO, SiN, or SiZrN can be doped with aluminum.

[0164] Table 3 summarizes the ratio of the thickness of the second electrically conductive layer 21.2 to the thickness of the first electrically conductive layer 21.1 (“21.2 / 21.1”), the ratio of the thickness of the second electrically conductive layer 21.2 to the thickness of the third electrically conductive layer 21.3 (“21.2 / 21.3”) and the ratio of the thickness of the first electrically conductive layer 21.1 to the thickness of the third electrically conductive layer 21.3 (“21.1 / 21.3”) for Examples 1 to 5 and the Comparative Example.

[0165] The comparative example differs from examples 1 to 5 in particular in the thickness of the electrically conductive layers 21.1, 21.2, 21.3. While the absolute thickness in examples 1 to 5 lies within the ranges according to the invention, the thickness of the third electrically conductive layer 21.3 in the comparative example is less than 10 nm and the thickness of the second electrically conductive layer 21.2 is more than 10 nm. The thickness ratios in examples 1 to 5 are within the ranges according to the invention. In the comparative example, however, the ratios “21.2 / 21.3” and “21.1 / 21.3” are more than 1.0.

[0166] Table 3

[0167] The dielectric layers have the following refractive indices at 550 nm: ZnO (2.00), SiN (2.00), SnZnO (2.05), SiZr17N (2.22), SiZr27N (2.40).

[0168] The optical thicknesses of the individual dielectric layers correspond to the product of the geometric thickness specified in the tables and the refractive index. The optical thicknesses of the entire dielectric layer sequences M1, M2, M3, and M4 correspond to the sum of the optical thicknesses of the individual layers.The optical thicknesses of the dielectric layer sequences M1, M2, M3, M4 for Examples 1 to 5 and the Comparative Example are summarized in Table 4, as are the ratio of the optical thickness of the second dielectric layer sequence M2 to the optical thickness of the first dielectric layer sequence M1 (“M2 / M1”), the ratio of the optical thickness of the second dielectric layer sequence M2 to the optical thickness of the third dielectric layer sequence M3 (“M2 / M3”), the ratio of the optical thickness of the second dielectric layer sequence M2 to the optical thickness of the fourth dielectric layer sequence M4 (“M2 / M4”), the ratio of the optical thickness of the first dielectric layer sequence M1 to the optical thickness of the third dielectric layer sequence M3 (“M1 / M3”), and the ratio of the optical thickness of the first dielectric layer sequence M1 to the optical thickness of the fourth dielectric layer sequence M4 (“M1 / M4”). Table 4.

[0169] Table 5 lists some physical parameters of the composite panes according to the invention (Examples 1 to 5) and the comparative example that are familiar to those skilled in the art and are typically used to characterize vehicle windows. RL stands for the integrated light reflection and TL for the integrated light transmission (according to ISO 9050). The information after RL or TL indicates the light source used, where A stands for light source A and HUD for a HUD projector with radiation wavelengths of 473 nm, 550 nm, and 630 nm (RGB). The RL HUD values ​​are given for both polarization directions (p-polarized and s-polarized). The angle specified after the type of light indicates the angle of incidence of the radiation to the outside surface normal. Angles of incidence less than 90° therefore indicate outside irradiation, and angles of incidence greater than 90° indicate interior irradiation.The specified angle of incidence of 115° corresponds to an angle of incidence of 65° (=180°-115°) to the interior surface normal and simulates irradiation with the projector according to the invention as the imaging unit 4. Below the reflection values ​​relative to the radiation of the HUD projector are the corresponding color values ​​a* and b* in the L*a*b* color space, followed by the light source used (HUD projector) and the observation angle (angle at which the light beam hits the retina in the eye). These values ​​are also listed for both polarization directions. TTS stands for the total irradiated solar energy, measured according to ISO 13837, and is a measure of thermal comfort. The RL HUD values ​​indicate the reflectance at the solar control coating 20, not the total reflectance of the laminated pane 10. They refer only to the reflection that occurred at the solar control coating.This occurs laterally offset from reflections from other surfaces (e.g., from glass surfaces in the case of s-polarized radiation) and can therefore be determined in isolation. The RL HUD values ​​thus provide a measure of the intensity of the ghost image caused by the solar control coating.

[0170] The composite panes were made of clear soda-lime glass and a clear PVB film as the intermediate layer 3. They were only equipped with the solar control coating 20 according to the invention; the values ​​given serve to characterize it. Even in the measurements with p-polarized radiation, no reflection layer 30 was present, which would be required in a HUD projection arrangement as in Figure 3.

[0171] Table 5

[0172] Table 5 shows that all composite panes 10 exhibited a light transmittance (TL A 0°) of more than 70% and are therefore suitable for use as a motor vehicle windshield. In Examples 1 to 5 according to the invention, a slightly higher light transmittance is observed than in the comparative example. The composite panes 10 according to the invention are also characterized by a lower outside reflectance (RL A 8°), which is advantageous for aesthetic reasons.

[0173] It can be seen in particular that the sun protection coating 20 in inventive examples 1 to 5 had a very low reflectance relative to the imaging unit 4 (RL HUD p-pol. 115°, RL HUD s-pol. 115°). Regardless of the polarization direction, the reflectance was always less than 5%. The sun protection coating 20 can be used for HUD projection systems with both s-polarized radiation and those with p-polarized radiation, with only a very low-intensity ghost image being generated by the sun protection coating 20. Significantly higher reflectance values ​​occur in the comparative example. Furthermore, the reflection colors are very neutral, so that no undesirable color cast is generated in the HUD projection. Very similar reflectance values ​​were also observed with the standard light source D65, always less than 5% in the inventive examples.

[0174] All laminated glass units 10 exhibit low TTS values ​​of less than 50%. The solar control coating 20 therefore significantly reduces energy input and significantly improves thermal comfort in the vehicle interior.

[0175] List of reference symbols:

[0176] (10) Composite pane

[0177] (1) Outer pane

[0178] (2) Inner pane

[0179] (3) thermoplastic intermediate layer

[0180] (4) imaging unit

[0181] (5) Viewer / vehicle driver

[0182] (20) Sun protection coating

[0183] (M1), (M2), (M3), (M4) 1st, 2nd, 3rd, 4th dielectric layer sequence

[0184] (21.1), (21.2), (21.3) 1st, 2nd, 3rd electrically conductive layer

[0185] (22.1), (22.2), (22.3), (22.4) 1st, 2nd, 3rd, 4th anti-reflective coating

[0186] (22a.1), (22a.2), (22a.3), (22a.4) 1st, 2nd, 3rd, 4th dielectric layer

[0187] (Refractive index < 2.1)

[0188] (22b.1), (22b.2), (22b.3), (22b.4) 1st, 2nd, 3rd, 4th optically highly refractive layer

[0189] (Refractive index > 2.1)

[0190] (22c.2) optically highly refractive layer (refractive index > 2.3)

[0191] (22d.2) additional optically highly refractive layer (refractive index > 2.1)

[0192] (23.1), (23.2), (23.3) 1st, 2nd, 3rd smoothing layer

[0193] (24.1), (24.2), (24.3) 1.. 2.. 3. first adaptation layer

[0194] (25.2), (25.3), (25.4) 1.. 2., 3. second adaptation layer

[0195] (26.1), (26.2), (26.3) 1.. 2.. 3. Blocker layer

[0196] (30) Reflective layer

[0197] (O) Upper edge of the composite pane 10

[0198] (U) Lower edge of the composite pane 10

[0199] (B) HUD area of ​​the composite pane 10

[0200] (E) Eyebox

[0201] (I) outside surface of the outer pane 1

[0202] (II) interior surface of the outer pane 1

[0203] (III) outer surface of the inner pane 2

[0204] (IV) interior surface of the inner pane 2

Claims

Patent claims 1. Projection arrangement for a head-up display, comprising - a composite pane (10) comprising an outer pane (1) and an inner pane (2) which are connected to one another via a thermoplastic intermediate layer (3), with a HUD region (B); and - an imaging unit (4) directed towards the HUD area (B); wherein the composite pane (10) is provided with a sun protection coating (20) which - a first dielectric layer or layer sequence (M1), - a first electrically conductive layer (21.1) with a thickness of 6 nm to 10 nm, - a second dielectric layer or layer sequence (M2), - a second electrically conductive layer (21 .2) with a thickness of 6 nm to 10 nm, - a third dielectric layer or layer sequence (M3), - a third electrically conductive layer (21.3) with a thickness of 10 nm to 15 nm and - a fourth dielectric layer or layer sequence (M4) arranged in the specified order starting from the substrate, wherein - the ratio of the thickness of the second electrically conductive layer (21.2) to the thickness of the first electrically conductive layer (21.1) is from 0.9 to 1.3, - the ratio of the thickness of the second electrically conductive layer (21.2) to the thickness of the third electrically conductive layer (21.3) is from 0.5 to 1.0 and - the ratio of the thickness of the first electrically conductive layer (21.1) to the thickness of the third electrically conductive layer (21.3) is from 0.5 to 1.

0.

2. Projection arrangement according to claim 1, wherein the sun protection coating (20) in the composite pane (10) has a reflectance of less than 5% compared to the standard light source D65 at an angle of incidence of 65°, both with s-polarized radiation and with p-polarized radiation.

3. Projection arrangement according to claim 1 or 2, wherein - the first dielectric layer or layer sequence (M1) has an optical thickness of 70 nm to 100 nm, preferably of 70 nm to 90 nm, - the second dielectric layer or layer sequence (M2) has an optical thickness of 130 nm to 200 nm, preferably 140 nm to 160 nm, - the third dielectric layer or layer sequence (M3) has an optical thickness of 130 nm to 200 nm, preferably 130 nm to 180 nm, - the fourth dielectric layer or layer sequence (M4) has an optical thickness of 90 nm to 150 nm, preferably of 90 nm to 120 nm.

4. Projection arrangement according to one of claims 1 to 3, wherein - the ratio of the optical thickness of the second dielectric layer or layer sequence (M2) to the optical thickness of the first dielectric layer or layer sequence (M1) is from 1.8 to 3.0, preferably from 1.9 to 2.5, - the ratio of the optical thickness of the second dielectric layer or layer sequence (M2) to the optical thickness of the third dielectric layer or layer sequence (M3) is from 0.8 to 1.2, preferably from 0.9 to 1.1, - the ratio of the optical thickness of the second dielectric layer or layer sequence (M2) to the optical thickness of the fourth dielectric layer or layer sequence (M4) is from 1.2 to 3.0, preferably from 1.3 to 2.0, - the ratio of the optical thickness of the first dielectric layer or layer sequence (M1) to the optical thickness of the third dielectric layer or layer sequence (M3) is from 0.3 to 0.8, preferably from 0.4 to 0.6 and - the ratio of the optical thickness of the first dielectric layer or layer sequence (M1) to the optical thickness of the fourth dielectric layer or layer sequence (M4) is from 0.5 to 1.0, preferably from 0.6 to 0.

8.

5. Projection arrangement according to one of claims 1 to 4, wherein - the thickness of the first electrically conductive layer (21.1) is from 7 nm to 9 nm, - the thickness of the second electrically conductive layer (21.2) is from 7 nm to 10 nm and - the thickness of the third electrically conductive layer (21.3) is from 10 nm to 13 nm.

6. Projection arrangement according to one of claims 1 to 5, wherein - the ratio of the thickness of the second electrically conductive layer (21.2) to the thickness of the first electrically conductive layer (21.1) is from 1.0 to 1.2, - the ratio of the thickness of the second electrically conductive layer (21.2) to the thickness of the third electrically conductive layer (21.3) is from 0.6 to 0.9 and the ratio of the thickness of the first electrically conductive layer (21.1) to the thickness of the third electrically conductive layer (21.3) is from 0.6 to 0.

9.

7. Projection arrangement according to one of claims 1 to 6, wherein the electrically conductive layers (21.1, 21.2, 21.3) are formed on the basis of silver.

8. Projection arrangement according to one of claims 1 to 7, wherein the sun protection coating (20) is arranged on the surface (II, III) of the outer pane (1) or the inner pane (2) facing the intermediate layer (3) or within the intermediate layer (3), preferably on the interior-side surface (II) of the outer pane (1).

9. Projection arrangement according to one of claims 1 to 8, wherein - the first dielectric layer sequence (M1) comprises an anti-reflection layer (22.1), a smoothing layer (23.1) and a first adaptation layer (24.1), - the second dielectric layer sequence (M2) comprises a second adaptation layer (25.2), an anti-reflection layer (22.2), a smoothing layer (23.2) and a first adaptation layer (24.2), - the third dielectric layer sequence (M3) comprises a second adaptation layer (25.3), an anti-reflection layer (22.3), a smoothing layer (23.3) and a first adaptation layer (24.3) and - the fourth dielectric layer sequence (M4) comprises a second adaptation layer (25.4) and an anti-reflection layer (22.4).

10. Projection arrangement according to claim 9, wherein - the anti-reflection coatings (22.1, 22.2, 22.3, 22.4) are based on silicon nitride and / or silicon zirconium nitride, - the smoothing layers (23.1, 23.2, 23.3, 23.4) are based on tin-zinc mixed oxide, - the adaptation layers (24.1, 24.2, 24.3; 25.2, 25.3, 25.4) are formed on the basis of zinc oxide.

11. Projection arrangement according to claim 9 or 10, wherein the anti-reflection layers (22.1, 22.2, 22.3, 22.4) are divided into at least one dielectric layer based on silicon nitride and at least one dielectric layer based on silicon zirconium nitride.

12. Projection arrangement according to one of claims 1 to 11, wherein the imaging unit (4) is operated with s-polarized radiation and wherein the intermediate layer is wedge-shaped so that its thickness increases in a direction from the lower edge (U) to the upper edge (O) of the composite pane (10).

13. Projection arrangement according to one of claims 1 to 11, wherein the imaging unit (4) is operated with p-polarized radiation and wherein the composite pane (10) is provided with a reflection layer (30) which is suitable for reflecting the p-polarized radiation of the imaging unit (4) to generate a display image.

14. Projection arrangement according to one of claims 1 to 13, wherein the imaging unit (4) irradiates the HUD area (B) with an angle of incidence of 60° to 70°.

15. Projection arrangement according to one of claims 1 to 15, wherein the composite pane (10) has a TTS value of less than 50%.

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